ZCZC MIATCDAT2 ALL TTAA00 KNHC DDHHMM TROPICAL STORM PHILIPPE DISCUSSION NUMBER 20 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 AM EDT THU SEP 22 2005 PHILIPPE REMAINS VERY DISORGANIZED...WITH THE DEEP CONVECTION IN SCATTERED CLUSTERS NEAR/AROUND THE ESTIMATED CENTER AND LITTLE EVIDENCE OF BANDING FEATURES. MY BEST GUESS IS THAT THE SYSTEM HAS WEAKENED TO A MINIMAL TROPICAL STORM. SHEARING AND SUBSIDENCE ASSOCIATED WITH A LARGE UPPER-LEVEL LOW CENTERED NEAR 23N 62W HAVE BEEN DISRUPTING THE TROPICAL CYCLONE. GLOBAL MODELS CONTINUE TO FORECAST THAT THE UPPER-LEVEL LOW WILL BE SQUEEZED INTO A CYCLONIC SHEAR AXIS...CREATING AN ANTICYCLONIC UPPER-LEVEL FLOW FIELD OVER PHILIPPE THAT WOULD ALLOW STRENGTHENING. HOWEVER I SEE NO SIGN OF THIS HAPPENING WITHIN THE NEXT DAY OR SO...AND THEREFORE NO CHANGE IN STRENGTH IS FORECAST FOR 24 HOURS WITH ONLY A MODEST INCREASE IN INTENSITY THEREAFTER. ANOTHER POSSIBILITY IS THAT...GIVEN ITS SOMEWHAT SUBTROPICAL APPEARANCE...THE SYSTEM COULD STRENGTHEN AS A HYBRID-TYPE OF CYCLONE. ASSUMING THAT PHILIPPE WILL INTERACT WITH A FRONTAL SYSTEM BY THE END OF THE PERIOD...THE FORECAST SHOWS EXTRATROPICAL TRANSFORMATION BY DAY 5. THE CENTER CANNOT BE IDENTIFIED WITH GEOSTATIONARY IMAGERY...AND I HAVE BASED THE LOCATION PRIMARILY ON A POOR FIX USING AN AMSU-B IMAGE. A RECENT AMSR-E IMAGE SUGGESTS THAT THE CENTER MAY BE LOCATED MORE TO THE NORTHEAST...BUT WE WILL WAIT FOR VISIBLE IMAGERY TO CONFIRM THIS. FOR THE TIME BEING...THE INITIAL MOTION ESTIMATE IS A HIGHLY UNCERTAIN 350/10. TRACK GUIDANCE CONTINUES TO INDICATE A MOTION AROUND THE WESTERN PERIPHERY OF A SUBTROPICAL HIGH PRESSURE CELL. THERE CONTINUES TO BE SOME UNCERTAINTY AS TO WHETHER PHILIPPE WILL BE PICKED UP BY A SHORTWAVE TROUGH MOVING OFF THE CANADIAN MARITIMES. SOME GLOBAL MODELS...E.G. THE GFS... INDICATE THAT AT LEAST A PIECE OF PHILIPPE'S VORTICITY WILL BE LEFT BEHIND IN THE SUBTROPICS. BECAUSE OF THIS UNCERTAINTY...THE OFFICIAL TRACK FORECAST IS A LITTLE SLOWER AND TO THE RIGHT OF THAT FROM THE PREVIOUS ADVISORY. FORECASTER PASCH FORECAST POSITIONS AND MAX WINDS INITIAL 22/0900Z 23.3N 57.2W 35 KT 12HR VT 22/1800Z 25.5N 57.8W 35 KT 24HR VT 23/0600Z 28.1N 59.0W 35 KT 36HR VT 23/1800Z 30.5N 60.0W 40 KT 48HR VT 24/0600Z 32.5N 59.0W 45 KT 72HR VT 25/0600Z 35.0N 54.0W 45 KT 96HR VT 26/0600Z 37.0N 48.0W 40 KT 120HR VT 27/0600Z 38.5N 41.5W 40 KT...EXTRATROPICAL $$ NNNN
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Page last modified: Thursday, 22-Sep-2005 08:40:11 UTC